The invention relates to an ion selective electrode in which an ion selective polymer layer is in contact on the one hand with the measuring liquid and on the other hand with a wire with low drift potential relative to the polymer layer.
Recently, ion selective electrodes have gained considerable importance for electrochemical measurement of various types, particularly in physiology (cf. K. Cammann, "Das Arbeiten mit ionenselektiven Elektroden", Springer-Verlag, Berlin, Heidelberg, New York, 1973). Solid membrane electrodes and liquid membrane electrodes are distinguished from one another. The wire-clad electrodes may be regarded as a further development of the latter (cf. K. Cammann, page 106). They consist of a thin platinum wire which is coated with a layer of polyvinylchloride (PVC). The PVC layer is saturated with the active phase, i.e. the ion selective substance. These electrodes are manufactured with an inner electrolyte in a simple manner in camparison with the normal liquid membrane electrodes, and are also layer or position independent. The selectivity ratio is more favourable than in corresponding liquid membrane electrode types, the pick-up time is very short and the life span is considerably higher than in normal liquid membrane electrodes.